Type of Document Dissertation Author Marinovici, Laurentiu Dan URN etd-05202011-111953 Title Communication-constrained Feedback Stability and Multi-agent System Consensusability in Networked Control Systems Degree Doctor of Philosophy (Ph.D.) Department Electrical & Computer Engineering Advisory Committee
Advisor Name Title Zhou, Kemin Committee Chair Gu, Guoxiang Committee Co-Chair Wei, Shuangqing Committee Member Wolenski, Peter Committee Member Sathivel, Subramanian Dean's Representative Keywords
- communication constrained feedback
- multi-agent systems
- logarithmic quantizer
- networked control systems
Date of Defense 2011-05-12 Availability unrestricted AbstractWith the advances in wireless communication, the topic of Networked Control Systems
(NCSs) has become an interesting research subject. Moreover, the advantages they offer
convinced companies to implement and use data networks for remote industrial control and
process automation. Data networks prove to be very efficient for controlling distributed
systems, which would otherwise require complex wiring connections on large or inaccessible areas. In addition, they are easier to maintain and more cost efficient. Unfortunately,
stability and performance control is always going to be affected by network and communication issues, such as band-limited channels, quantization errors, sampling, delays, packet
dropouts or system architecture.
The first part of this research aims to study the effects of both input and output quantization on an NCS. Both input and output quantization errors are going to be modeled as sector bounded multiplicative uncertainties, the main goal being the minimization of the quantization density, while maintaining feedback stability. Modeling quantization errors as uncertainties allows for robust optimal control strategies to be applied in order to study the accepted uncertainty levels, which are directly related to the quantization levels. A new feedback law is proposed that will improve closed-loop system stability by increasing the upper bound of allowed uncertainty, and thus allowing the use of a coarser quantizer.
Another aspect of NCS deals with coordination of the independent agents within a Multi-agent System (MAS). This research addresses the consensus problem for a set of discrete-time agents communicating through a network with directed information flow. It examines the combined effect of agent dynamics and network topology on agents' consensusability. Given a particular consensus protocol, a sufficient condition is given for agents to be consensusable. This condition requires the eigenvalues of the digraph modeling the
network topology to be outer bounded by a fan-shaped area determined by the Mahler
measure of the agents' dynamics matrix.
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